Electret microphone

摘要

A back plate having a recess in an underside thereof and a stationary back electrode at a central portion thereof is secured to a substrate, a spacer having an opening is mounted on the back plate so as to form a vacancy between an inside wall of the opening and a periphery of the stationary back electrode. A diaphragm electrode is provided on the spacer. The back plate has vents in the vacancy so as to communicate a space between the back electrode and the diaphragm electrode to a space in the recess of the back plate.